// Number:对象的值转换为数字。无法转就是NaN
console.log(Number(new Boolean(false)), Number(new Boolean(true))); // 0 1
console.log(Number(new Date())); // 时间戳毫秒数
console.log(Number(new String("999"))); // 999
console.log(Number(new String("999 888"))); // NaN
